You should do it. I was in a similar situation a couple years ago...I was at WDW for a work conference and was offered this exact same offer. It had to be prebooked/paid, and after I looked at my conference schedule before I left home I passed on the offer using the same thinking (I would only be able to go one day after 4pm and is $68 bucks worth spending 4-6 in Magic Kingdom?!). Oh, I'm still kicking myself about passing the offer up. Once I got to the conference and was right there at disney on property it killed me that I didn't have any tickets to go into Magic Kingdom for a half a day. I even went to guest relations and the TTC to see if I could still get the offer. Sadly, I couldn't so I was out of luck and really disappointed. I didn't have my family with me on this trip so I know I would have been even more disappointed knowing my family was in MK having fun and I wasn't. So, I would do it. BUT, if you decide against it and want to still get some Disney magic, you could still visit DS (DTD at the time), or do what I did...Since I couldn't go into a park, I ended up hopping on the monorail and visited the 3 monorail resorts to explore and shop, had dinner at Kona at the Poly and watched Wishes from the Poly's beach. So that could be an alternative for your family if you don't want to buy the ticket but still want to enjoy some disney family time. It ended up being a great night, but it did break my heart to be SO CLOSE to MK and not be able to actually go INSIDE. If I had to do it over, I would have gladly bought that one-day-after-meeting ticket.